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Mix-substituted phthalocyanines of a “push–pull”-type and their metal complexes as prospective nanostructured materials for optoelectronics

Usol'tseva N. V., Smirnova A. I., Kazak A. V., Giricheva N. I., Galanin N. E., Shaposhnikov G. P., Bodnarchuk V. V., Yablonskii S. V.

Opto-Electronics Review

2017

Vol. 25, No. 2

127--136

To study the influence of structural features of phthalocyanine (Pc) derivatives on their physico-chemical properties in bulk and thin films, 23 new phthalocyanines with different quantity and ratio of donor (alkyloxy-groups, in fragment “A”) and acceptor (Cl-, in fragment “B”) substituents in one molecule of the A3B, ABAB and AABB types with varied length of alkyloxy-substituents and their metal complexes were designed and synthesized. A comparative analysis of spectral, mesomorphic and photoelectric properties of these mix-substituted phthalocyanines of a “push–pull” type was performed. It was shown that non-peripheral substitution by alkyloxy-fragments in hetero-substituted Pcs (similar to homo-substituted Pc) leads to red-shifting of the Q-band into near-IR region. The intensity of photoluminescence, position of peaks and their splitting are strongly connected with chemical structure of Pcs and the type of solvent. In contrast to non-mesogenic octyloxy-Pc (A4) having alkyloxy-substituents in non-peripheral positions, 22 of 23 synthesized compounds possess columnar mesomorphism. The change of donor–acceptor ratio can influence the type of mesophase. A new approach to the creation of materials for optoelectronics is proposed and implemented, which includes design of compounds possessing vitrification from mesophase with maintenance of a columnar order, absorption in the near IR-region of the spectrum and good performance electrophysical characteristics simultaneously.

Photoelectric properties of HgMnTe photodiodes with ion etched p-n junctions

Kosyachenko L. A., Rarenko I. M., Weiguo S., Zengxiong L., Qibing G.

Opto-Electronics Review

2000

Vol. 8, No. 3

251-262

Thotodiodes with p-n junctions formed by ion etching of p-Hg1-xMnxTe (x ≈1) are reported. The multielement photodiode arrays for mid-infrared region were fabricated using surface passivation, photolithography and three-layer metallisation processes. The absorption curves of the crystals found from optical measurements are treated within the Kane theory for semiconductors with highly nonparabolic energy bands. The parameters of the diodes are obtained from their electrical study. It is shown that due to strong degeneracy of the n+ - layer the Hg1-xMnxTe diode structure can be considered as one-sided abrupt n+ -p junction with the barrier height larger significantly than the semiconductor bandgap. The diode responsivity spectra are interpreted in the framework of model taking into account the generation of photocarriers in n+ - and p-regions as well as in the depletion layer. The diode photoresponsivity in the region of the photon energies below semiconductor bandgap is shown to be caused by the gentle slope of the observed absorption edge. Temperature measurements reveal essential peculiarities of carrier tunnelling in the diodes. Invoking the general expression for the tunnelling probability and taking into consideration the opposing flow of electrons allow the observed tunnelling decay at low reverse biases to be explained. The zero bias resistance-area product (RoA) for the Hg1-xMNxTe diodes with cutoff wavelengths 7-8 and 10-11um amount up to 20-30 and ~ 500 Ω cm2, respectively, indicating the photodiodes under study to be competitive with Hg1-xCdxTe photovoltaic detectors.